Variability of Denosumab densitometric response in postmenopausal osteoporosis.

The objective of our prospective study is to specify the variability of densitometric response to Denosumab, given in the second line, and to try to understand the reasons. All menopausal patients with primary osteoporosis, treated by Denosumab in our centre from 2014 to 2015, were included in this open prospective work. At T0, the patient's age, type of fracture, and previous treatments were collated. At T0 and T1, after 1 year of treatment by Dmab, a DXA of the spine and the hip and a determination of CTX were performed. Sixty-three patients aged 68.8 ± 8.3 years were included. The median number of treatments prescribed for osteoporosis before switch to Denosumab was 2.4. The median duration of these treatments was 7.2 years. At T1, CTX was less than 33 pg/ml (minimum threshold for our assay kit) in all patients. The median BMD in the spine increased by + 5.44% compared to T0. 14 patients in the upper quartile had a median BMD gain in the spine of + 11.07%. Fourteen patients in the lower quartile had a median BMD gain in the spine of + 0.6%. Only the duration of previous treatments, which was greater in the non-responder group, differed between these two groups. In the total cohort, the spinal densitometric gain was negatively correlated with the age of the patient at baseline (p = 0.04), the duration of previous treatment (p = 0.02), and positively with the CTX level (p = 0.05). The Dmab densitometric response is highly variable, partly explained by the duration of previous treatments and the level of bone resorption at initiation of treatment.